Improve Documentation: Moveit Task Constructor

[cpetersmeier]

Description

The tutorial for the Moveit Task Constructor provides a great introduction on how to get started and covers core concepts in a detailed manner.

However as a new user, whilst the demo code is well documented, one might want to have a more accessible version of the "Pick and Place" tutorial. Additionally, it would be great to have a "blueprint" example of core class derivatives with example implementations of e.g. compute functions.

In this manner, the additions of this Pull Request aim to extend the Moveit Task Constructor Tutorial in the following ways:

• Programmatic extension of stages.
• Stage configuration using properties.
• Detailed discussion of the Pick and Place task.

I would really appreciate some feedback and would love to incorporate that and any further additional ideas in the tutorial code!

[welcome[bot]]

Thanks for helping in improving MoveIt and open source robotics!